Abstract
In the previous report, the present authors have proposed the following modified Miner's equation for the fatigue-lifes of specimens under varying stress amplitude in two stages.
n1/N1+αn2/N2=1 (a)
In this paper, they investigated on the value of α and showed that the value of α is the function of the cycle ratio, the stress level of the primary and secondary stress, etc.. Especially, when the secondary stress is higer than the primary one, the value of α could be expressed only by the function of the cycle ratio of the primary stress as follows:
α=1-n1/N1 (b)
Moreover, they investigated how the hardness of the specimens varied with the fatigue loading. When the load was transformed from any primary stress level to a higher secondary stress level, the values of hardness on the surface of specimens increased up to a constant value corresponding with the stress level.
But when the secondary stress level is lower than the primary one the value of hardness obtained after the repetition of the primary stress, varied little. And they introduced the equation (b) to approximately show the relation between the fatigue-life and the hardness-variation.
